In process plants, most new field instruments that sense or control parameters for processing chemicals and pharmaceuticals are smart devices. A smart device is microprocessor-based, has extra functionality and digital compensation, and supports multiple sensor types or multiple variables. The smart device includes one or more transducers that sense real-world parameters such as temperature, pressure, flow or position and output electrical signals representative of the sensed values.
A smart device communicates with other devices, such as communicators and calibrators using one or more industry accepted standard protocols such as HART, an acronym for Highway Addressable Remote Transducer, or Fieldbus. HART is an industry standard for a hybrid protocol that enables communications between smart field devices and a control system that employs legacy 4-20 mA wiring. Foundation Fieldbus is another all-digital protocol. These and other protocols use device descriptions that are stored in the smart device. The protocols enable process plant managers to mix instruments of different manufacturers.
Smart devices hold one or more blocks or functional units. A functional unit has an input, an output, or a control function. Each block has one or more parameters associated therewith. A parameter is an attribute which characterizes, affects, or is otherwise related to a block or a device. Exemplary parameters include the kind of block or kind of device, the maximum operating or measurement range of a block or a device, the mode of a block or a device, the value of a block or a device measurement, etc. In addition, parameters have one or more properties, such as the name of the parameter (e.g., temperature), the value of the property (e.g., measured temperature), and the property of units involved in the measurement (e.g., degrees Fahrenheit or centigrade).
Each smart device has a computer memory that holds a Device Description (DD). The DD includes information about the smart device and is also a device driver computer program for operating the smart device. Device Descriptions (DDs) provide the information needed by a communicator, calibrator, host application, or control system to properly access and display important device information located in smart devices. The DD includes all of the information needed to fully communicate with the communicator and all parametric information about the smart device. For example, the DD contains information about the smart device including its tag (an arbitrary name and location assigned to the instrument), basic parameters it monitors such as its primary variable (temperature, pressure, flow, position, etc.), and secondary and tertiary parameters and other preferred parameters of interest and importance to processing control. The communicator or calibrator reads the DD and uses the DD to navigate through the smart device to gather information including the tag (name/location) of the device, its primary variable, primary parameters, and secondary or tertiary parameters or other preferred parameters.
Many smart devices are equipped with wireless transceivers in addition to conventional wired communication ports. When processing plants and facilities expand or are otherwise remodeled, it is common to use wireless smart devices for communicating with a communication center. It is often less expensive and quicker to establish a wireless network.
Wireless communications systems, in combination with a communication center and smart devices, allow operators of complex processes to set up, change, monitor, and automate complex processes. Each smart device may be individually controlled by commands issued from the communication center. That center synchronizes the operations and communications of all smart devices in the network. The smart devices are synchronized to report their status at set times during a broadcast portion of a communication cycle. The communications cycle leaves open one or more time slots for acyclic communication between the individual devices and the communication center. The communication network also provides for interruptions of synchronous transmissions for alarms sent by a smart device to indicate a potentially dangerous condition. If the communication center does not receive an expected status signal from a smart device, the communication center may attempt to directly communicate with the non-transmitting device.
When the communication center fails to receive an expected status signal, such failure does not always mean the smart device is not functioning. It is possible that electromagnetic noise in the vicinity of the smart device is interfering with its communication to its access point. Alternatively, one or more access points or nodes for relaying the status of the smart device may have failed. Nevertheless, it would be dangerous to continue to operate a process without knowledge and control of the smart devices, especially those that are critical to safe operation. In such cases, a technician may be dispatched to inspect the smart device and to determine whether it is working or there is a network communication problem. If inspection of the smart device indicates it is operating as expected, the process may continue. Accordingly there is a need for a tool to analyze the wireless network and check the wireless output of a smart device at the locale of the smart device.